This lesson explains the types of careless errors that cost marks in IGCSE Physics and how to prevent them.
Why silly mistakes matter
A student who knows the content can still lose 10 to 15 marks per paper through careless errors. That is the difference between an A and a C.
Error type 1: Misreading the question
The question says “calculate the deceleration” but you calculate the acceleration and give a positive answer. The question says “state two differences” but you give one.
Fix: Underline the command word and the number of points required before you start writing.
Error type 2: Unit conversion
The question gives distance in cm but the formula needs metres. You substitute 50 instead of 0.5.
Fix: Write all given values in SI units before substituting into the equation.
Error type 3: Wrong formula
You use v = f lambda when the question asks about the speed of a car (v = d / t).
Fix: Read the question, identify the physics topic, then select the formula. Write the formula before substituting.
Error type 4: Calculator entry
You enter 3.2 x 10 x 8 instead of 3.2 EXP 8.
Fix: Double-check every standard form entry. If the answer is unexpectedly large or small, re-enter.
Error type 5: Missing the unit
You calculate 75 J but write only “75.” The unit mark is lost.
Fix: Write the unit immediately after every calculation. Make it a habit.
Error type 6: Not reading the graph properly
You read the y-value at x = 3 as 15 when it is actually 16, because you miscounted the grid lines.
Fix: Count the grid divisions between two labelled values to find the scale. Then count carefully from the nearest label.
Error type 7: Rounding too early
You round an intermediate answer to 1 significant figure and use that in the next step, introducing a large rounding error.
Fix: Keep all digits until the final answer.
A 30-second check routine
After every calculation question, check: (1) correct formula? (2) SI units? (3) correct substitution? (4) reasonable answer? (5) unit written?
Need a Plan Based on Actual Work?
A private taught trial can help distinguish whether the repeated difficulty is mainly Physics knowledge, Mathematics, practical reasoning or exam technique before regular lessons are discussed.